This report presents the results from the second phase of a longitudinal study of Americans' knowledge and feelings about agricultural biotechnology and how those perceptions and attitudes have changed over time. Two independent national probability samples of 1,200 adults were interviewed by phone in the spring of 2001 and 2003. While this report focuses on the findings from 2003, longitudinal comparisons are presented where appropriate. The report begins with an investigation of Americans' awareness of the presence of genetically modified (GM) ingredients in the foods they encounter everyday. Next, the report describes Americans' actual and perceived knowledge of science, biotechnology and food production. It then examines American opinions about GM foods in general, along with their opinions on a variety of existing and potential GM food products with direct or indirect consumer benefits. The report discusses the relationship between opinions of GM food and a variety of factors, including demographics, knowledge of biotechnology, purchasing behaviors and styles of food selection. Finally, it describes Americans' thoughts on GM food labeling. Highlights of the findings are below. Americans pay little attention to agricultural biotechnology. - Only half of Americans are aware that foods containing genetically modified (GM) ingredients are currently sold in stores. - Despite the prevalence of such foods, only one-quarter of Americans believe they have eaten them. - Little more than a third of Americans have ever discussed biotechnology. - Awareness, although still low, has increased slightly from 2001. Americans do not have much knowledge about agricultural biotechnology. - Self-reported knowledge of biotechnology is low. - Quizzes on biotechnology and food production reveal that Americans are generally uninformed about both, and this has not changed since 2001. Opinion on the acceptability of GM foods is split. - When asked directly, about half of Americans report that they approve of plant-based GM foods, (down from 2001) and about a quarter approve of animal-based GM foods (unchanged from 2001). - Approximately 10% of Americans report being unsure of their opinion of GM foods. Opinions of GM food are easily influenced. - Approval increases when specific benefits of GM food are mentioned. - Reactions to the technology depends on what it is called. The term biotechnology evokes the most positive responses, while genetic modification is perceived most negatively and genetic engineering is most often associated with cloning. Demographics and styles of choosing food are related to acceptance of GM foods. - Women, people over 64, and people with low levels of education are less likely to approve of GM foods. - People who value naturalness and healthfulness in their foods are slightly less likely to approve of GM foods. - People who have purchased organic foods in the past are less likely to approve of GM foods.